1. Field of the Invention
The present invention relates to ultrasonic transducer control, and particularly to a pulser logic method and system for an ultrasound beamformer utilizing minimal logic blocks in a field programmable gate array (FPGA).
2. Description of the Related Art
A travelling plane wave will tend to spread from the edges as it travels using a process of diffraction. This phenomenon is described by the Huygens-Fresnel principle, which describes each point on a wave front as a source for an expanding radial wave. As the wave expands, its energy is spread across a greater region. The further the wave has traveled, the greater the reduction in wave amplitude, and the greater the reduction in amplitude of any reflections from the wave. In order to create a high amplitude wave-front (to improve the echo strength), the energy from the wave can be focused. Focusing the wave controls the travel path of the acoustic energy so that its signal strength is maximized within a desired region. A transducer is any object that transforms energy from one type to another. In ultrasound, electrical energy is transformed into acoustic energy, and the reverse. Yet this energy needs to be focused. Typically, ultrasound transducers are geometrically focused, which means that the focal point is determined by the curvature of the transducer. With this type of transducer the focal point cannot be easily changed, and for this reason geometrically-focused transducers have limited use in a clinical setting.
A newer type of ultrasound transducer divides the transducer surface into sub-regions, each having an element in an array that can be separately controlled so that the elements in a transducer array are excited at different times (by adjusting the pattern of delay times) to focus the ultrasound beam. This is called transmit focusing. The beam may be focused straight ahead, or by skewing the transmit delay pattern so that the beam is no longer symmetric about the central axis of the transducer, the beam may be steered at an angle. Conventional, the pattern of pulses has been controlled by 16-bit binary counters. While effective, it would be desirable to accomplish transmit focusing using less memory at a faster overall speed.
Thus, a pulser logic method and system for an ultrasound beamformer solving the aforementioned problems is desired.